Various arrangements for simultaneous treating both sides of rotor blades have been suggested in the patent literature.
For example, EP 1 517 033 A1 discloses an apparatus for cleaning oblong objects, such as rotor blades. The apparatus of EP 1 517 033 A comprises two spaced apart main brush devices between which a washing zone is defined. Each brush device is substantially cylindrical in shape having a longitudinal axis, and being rotatable about said longitudinal axis. Each brush device is attached at least in one of its ends to an intermediate frame. One of the attachments comprises hinge means which allows the brush device to pivot in order to ease access to the washing zone.
WO 03/048569 discloses a method and an apparatus for treating a surface of a rotor blade mounted on a wind turbine. The apparatus suggested in WO 03/048569 is adapted to be moved relative to the surface of the rotor blade to be treated. According to WO 03/048569 various forms of treatments, such as washing, finishing and sealing, of a rotor blade mounted on a wind turbine may be carried out.
EP 1 517 033 A is only concerned with cleaning or washing of oblong objects, such as rotor blades for wind turbines. WO 03/04569 is beside cleaning also concerned with other types of treatments of rotor blades. Such other types of treatments could be finishing, painting and sealing. However, WO 03/04569 is only concerned with treatment of rotor blades already mounted on a wind turbine. Thus, WO 03/04569 is only concerned with service aspects of already mounted rotor blades on wind turbines.
Thus, none of the above-mentioned patent applications are concerned with manufacturing of rotor blades in that both EP 1 517 033 A and WO 03/04569 are concerned with service and/or repair of already mounted rotor blades.
One of the most time consuming processes in connection with manufacturing of rotor blades is related to surface treatment of rotor blades prior to painting the rotor blades. The reason for this being that one has to be sure that the surfaces of rotor blades are smooth thereby ensuring that desired aerodynamic properties of the rotor blade are met. In addition, due to considerations regarding generated noise from wind turbines it is of great importance that the surfaces of rotor blades are smooth.
In the field of rotor blade manufacturing it is generally accepted that surface treatment of rotor blades prior to painting is performed as a manual grinding process where a grinding device is manually moved across the surfaces of the rotor blade. As previously stated this is a very time consuming process. To exemplify it takes 15-20 hours for one person to grind both surfaces of a 44 meter long rotor blade. Another disadvantage related to manual grinding of rotor blades is the lack of uniformity of the grinding process.
Therefore, there is a need for optimizing treatments of wind turbine rotor blade surfaces, and at the same time reduce the time required for treating rotor blades.
Thus, it may be seen as an object of the present invention to comply with the above-mentioned needs.